1. Field of the Invention
This invention relates to a sign post construction that includes a breakaway joint for safety purposes. Specifically, the sign post of the present invention is constructed of a lower channel section, to be anchored in the ground or other substrate, connected to an upper channel section by means of a nested splice connection which breaks under predetermined force.
2. Prior Art
Sign posts of the breakaway variety have been utilized on the roads in the United States for many years. Federal, State and local governments require that sign posts and other structures associated with road construction be of a type specifically designed to ensure the safety of motorists in the event of a collision. Specifically, the Federal Highway Administration (FHWA) sets the standards and oversees the design and construction of safety sign posts on Federal highways.
As determined by tests, and based on years of experience, breakaway sign posts have proved to be highly effective in reducing vehicle damage and preventing severe injury or death to occupants of vehicles that have collided with highway marker signs utilizing safety sign posts.
One particular type of sign post has been used extensively, especially for use with stop signs and other smaller type signs. This post is constructed of steel channel having a hat-shaped cross-section with a flat, longitudinal center web and angularly outwardly divergent side walls. The center web has spaced apart holes along its entire length to allow mounting of a sign to the post at a selected height with one or more suitable fasteners, such as bolts or screws. During installation, the sign post of this type is driven in the ground with a sledge hammer, for example, followed by mounting of a sign to the post by a bolt type fastener.
The hat-shaped cross-section provides sufficient structural strength to allow the post to be driven into the ground. Further, the sign post of this type includes two flat, substantially coplanar edge flanges which provide secure mounting surfaces for engaging with the back of the sign when assembled.
The prior art includes a number of sign posts utilizing the above-described hat-shaped cross-sectional steel post with various types of breakaway connectors. The breakaway connector is typically provided between a section of post driven into the ground and a section of post extending above the ground and supporting the sign. During a collision with a motor vehicle, the section of the sign post above the ground is typically sheared off or hinged over to allow the motor vehicle to continue on its path with minimum damage to the vehicle and/or the absence of injury to the occupants of the vehicle.
Because of the cross-sectional shape of such sign posts, the angularly divergent side walls of the nested together upper and lower channel sections generally contact one another first, while the center webs of adjoining post sections remain spaced apart. This can lead to the imposition of stresses or deformations in the channel sections when they are fastened together by fasteners extended through the webs, resulting in unpredictable behavior of the post, and perhaps failure to break in the intended way when struck by a vehicle.
Moreover, it is difficult and awkward for one person to assemble a sign post from upper and lower sections, as described, since that person must extend multiple fasteners through the lower section, hold the upper section in proper orientation while positioning it over the fasteners, without dislodging the fasteners, and then secure the fasteners by placing and tightening washers and nuts on them, for example, all while holding the upper post section in proper upright position.